An air conditioning system which utilizes a filter assembly includes devices which cool, heat, dehumidify, humidify, and clean air flowing through it. The air conditioning system uses a filter installed at an intake portion located at the front face of the system. The filter prevents the entry of foreign particles entrained in the indoor air flowing into the system for treatment. Such a filter is usually of a rectangular shape and comprises a filter batt which is usually a cloth material. After a predetermined time particulate matter clogs the surface of the filter requiring that the filter be cleaned. The air conditioning system is generally positioned at a point higher than a user's height, i.e. proximate the ceiling, so as to perform most efficiently. In removing the conventional dust laden filter from the air conditioning system with an unprotected surface, dust is scattered on the person effecting the removal thereby eliciting an unpleasant feeling and causing an unhealthy environment. To collect falling dust a prior art filter provides a collector integrally formed at a bottom frame thereof. Such a typical structure is disclosed in Japanese Patent Laid-Open No. 1985-175937. However, a problem occurs in that dust laden on the surface of the filter is scattered during the removal with even a slight jarring of the filter. Japanese Patent Laid-Open No. 1985-62525 discloses another structure for preventing the dispersion of dust. Nevertheless, this has a problem in that microscopic particles cannot be caught by the filter and the finer dust on the rear surface of the filter is scattered throughout all the directions.